Etymology: L, immunis, free from; complexus, embrace; Gk, hyper, excess; L, sentire, to feel
a complement-dependent, immediate-acting humoral hypersensitivity to certain soluble antigens. It occurs when antibodies (immunoglobulin G or M) bind to circulating antigens, forming immune complexes. These complexes are deposited in tissues, such as blood vessels and renal glomeruli. Augmented by complement activation, they induce injury or dysfunctional responses in those tissues. Immune complex hypersensitivity is a dynamic, ever-changing process. Also called type III hypersensitivity. Compare anaphylactic hypersensitivity, cell-mediated immune response, cytotoxic anaphylaxis.